Indian Journal of Geo Marine Sciences Vol. 46 (06), June 2017, pp. 1098-1104 Comparative taxonomic evaluation of Thais species (Order: Gastropoda; Family: Muricidae) of Mollusca from Maharashtra coast of India Ravi Kumar1, A.K. Jaiswar1, S. Jahageerdar1, S.K. Chakraborty1, A. Pavan Kumar1 & Laxmi Prasad2 1 Central Institute of Fisheries Education (ICAR), Mumbai, Maharashtra - 400061, India Narendra Dev University of Agriculture & Technology, Kumarganj, Faizabad, U.P. -224229, India 2 [Email- akjaiswar@cife.edu.in] Received 17 December 2014 ; revised 15 November 2016 Based on shell morphology alone, it was difficult to differentiate the species belonging to genus Thais because of large amount of plasticity, observed in the shell characters. The colour of the shells was poorly defined as species identifying character in Thais species. The morphometric and meristic characters of the shell along with radular characters can solve the taxonomic ambiguities in Thais species (Thais lacera; T. blanfordi; T. tissoti; T. rudolphi; T. bufo and T. subnodulosa). The radular morphology was found to be different in each species except in T. rudolphi and T. blanfordi and hence these two species were differentiated based on radular morphology where the first denticle on outer base of the lateral cusp was smaller than other five denticles in T. rudolphi but in T. blanfordi, all were same in size. A deep ‘V’ shaped notch was present between inner denticle base of lateral cusp and central cusp in T. blanfordi, which was found to be a species specific character. [Keywords: Thais, Muricidae, Gastropods, Mollusca, radular] Introduction Molluscs have been evolved about 500 million years ago during the Cambrian period1. Among the classes of Mollusca, Gastropoda is most diverse group consisting of 80 per cent of all the molluscs numbering to around 80,000-100,000 species. Appukuttan, reported 3271 species belonging to 220 families and 591 genera, including 1900 species of gastropods, 1100 pelecypods, 210 cephalopods, 41 polyplacophores and 20 scaphopods from India2. Among the gastropods, muricids shell exhibits highest degree of variations with regards to shell morphology and sculptural patterns, which demonstrate its evolutionary importance3. Taxonomic studies of the gastropods have been carried out by researchers using shell morphology, sculpture, micro-structure, radula and anatomical characters, operculum structure and meristic counts. In Thais species the radula is stenoglossan (rachiglossan) type and usually has three cusps and smaller denticles. Radular characters have also been widely used in species diagnosis4,and, considered as valid indicators of phylogeny for Thaidid gastropods5. In India molluscan fishery is contributing significantly in total marine fishery. They form an important part of food of coastal population, in preparation of decorative items and in lime industry, and are important link in marine food web. However, the previous studies did not explain in detail taxonomy for majority of Thaidids, which aid to differentiate them easily. In view of this, the present study attempted to describe the identification of six Thais species occurring along the Maharashtra coast of India based on shell morphology and radular structure. Materials and Methods For the present study, a total of 177 specimens belonging to six different species of Thais comprising of Thais lacera (41); T. blanfordi (50); T. tissoti (50); T. rudolphi (20); T. bufo (10) and T. subnodulosa (6) were collected from different coastal areas, Juhu Kolivada, Bandstand, Aksa beach, Versova beach, Shrivardhan, Alibaug and Ratnagiri along the Maharashtra coast of India. The species were identified by using identification INDIAN J. MAR. SCI., VOL. 46, NO. 06, JUNE 2017 keys and publications1, 2-10. A total of seven morphometric characters, shell length (SL), shell width (SW), body whorl length (BWL), aperture length (APL), aperture width (APW), shell weight (SWT) and animal weight (AWT) were measured from the collected specimens. Similarly, four meristic traits like number of whorls (NW), number of primary spiral cords bearing nodules/tubercles on body whorl (NPBW), number of ridges or teeth inside of outer lip of the aperture (NRL) and number of tubercles in first spiral row on shoulder of body whorl bearing nodules/tubercles (NT) were counted. The length (mm) variables were measured using digital Vernier callipers and weight (g) with a digital weighing balance. Fig 1. (A). T. Lacera (i). six whorls, (ii). two spiral ridges on body whorl bearing strong triangular tubercles. (B) (i). two grooved sulcus instead of anal sulcus, (ii). Well developed umbilical chink; (2). T. rudolphi (C) (i).five whorls, (ii). Five primary spiral cords on body whorl, (D) (i).primary spiral cords bearing alternate brown and white nodules; (3). T. subnodulosa (E) (i).six whorls, (ii). A white spiral strip between third and fourth spiral cords on body whorl (F) (i). four ridges or teeth inside of outer lip of the aperture; (4). T. tissoti (G) (i).five whorls, (ii). secondary grooved spiral cords in between of the each primary spiral cord on body whorl, (H) (i). four primary spiral cords, (ii). five ridges or teeth inside of outer lip of the aperture; (5). T. bufo (I) (i).five whorls, (ii).two primary spiral cords bearing blunt tubercles; (6). T. blanfordi (J) (i).five whorls, (K) (i). ). six ridges or teeth inside of outer lip of the aperture. Extraction of radula Live specimens were anesthetized by injecting 7.5% of MgCl2 to relax, loosen the muscles attached to the inner shell surface, facilitated easy 1099 removal of animal out of shell without any damage. In case of any difficulty to draw out the animal from shell, the shells were kept in deep freeze at -200C for 24 hours resulting in shrinkage of muscle part. It is necessary to thaw them for 15-20 minutes in tap water before pulling out animal from frozen shells. Subsequently the extracted animals were washed and cleaned thoroughly; an incision was made on dorsal surface of the head with the help of scalpel and scissor, a few millimetres away from the base of tentacles or mouth opening to expose out radular sac. The sac was lifted out carefully with the help of forceps and transferred to 20% NaOH solution. Later the solution was boiled for 5-8 minutes at 1000C in order to dissolve the attached tissue that resulted in release of radula into the solution. The radula was picked up from solution with the help of forceps and washed in distilled water and absolute alcohol for 2-3 times to dehydrate and clean the radula. For further examination, the radulae were mounted on a clean glass slide with a drop of glycerine and examined under compound microscope. The radula was photographed by fixing the target at maximum resolution with provided zooming power (10X & 40X) followed by fixing the lens of digital camera on the eyepiece of compound microscope. Fig. 2 Characteristics of radula, 1. T. blanfordi, 2.T. bufo, 3. T. lacera, 4. T. rudolphi, 5. T. subnodulosa and, 6. T. tissoti cc- central cusp, lc- lateral cusp, idlc- inner denticle on lateral cusp, mc-marginal cusp, ddenticles between marginal and lateral cusp. Statistical analysis PROC MEANS procedure (SAS Institute, 2012) was used to estimate the descriptive statistics. PROC FREQ procedure was used to create frequency and cross-tabulation tables for meristic traits. 1100 KUMAR et al.: COMPARATIVE TAXONOMIC EVALUATION OF THAIS Table.1: Descriptive statistics of the morphometric traits Statistics Mean±SE Minimum Maximum Variable T. subnodulosa T. tissoti SL 18.25±1.306 18.15±0.400 BWL 12.23±0.745 9.84±0.282 SW 9.27±0.769 11.31±0.189 OPL 10.49±0.637 9.40±0.299 OPW 3.46±0.279 5.12±0.128 SWT 1.78±0.401 1.12±0.088 AWT 0.19±0.030 0.16±0.011 SL 14.23 10.84 BWL 9.92 6.86 SW 6.85 7.14 OPL 8.42 6.31 OPW 2.66 3.67 SWT 0.63 0.21 AWT 0.10 0.06 SL 21.78 26.27 BWL 13.97 14.97 SW 11.41 15.92 APL 12.19 14.75 APW 4.31 7.39 SWT 3.19 3.59 AWT 0.27 0.39 Species T. lacera 41.82±1.367 29.99±1.043 26.65±1.006 24.97±0.713 11.33±0.364 13.19±1.0458 2.17±0.154 25.55 18.75 17.02 17.19 7.42 2.58 0.87 58.76 41.54 39.68 32.91 15.72 22.43 4.07 T. rudolphi 45.18±3.134 37.08±2.481 28.45±1.752 33.60±2.209 14.09±0.887 13.49±2.035 3.68±0.682 27.14 20.91 17.04 19.49 6.62 2.94 0.59 70.57 53.07 41.58 47.65 20.07 35.92 8.83 T. blanfordi 26.03±0.373 18.22±0.281 15.42±0.207 15.55±0.207 6.76±0.118 3.09±0.125 0.36±0.015 19.11 14.58 12.18 12.75 5.06 1.35 0.14 29.83 21.96 19.05 18.45 8.32 4.59 0.56 T. bufo 38.64±3.893 32.22±3.723 27.16±3.413 29.52±3.417 12.97±1.641 12.71±4.588 3.31±1.620 27.14 20.91 17.04 19.49 6.62 2.94 0.59 60.85 53.89 47.56 47.61 22.49 47.31 15.91 Where, SL (Shell Length), SW (Shell Width), BWL (Body Whorl Length), APL (Aperture Length), APW (Aperture Width), SWT (Shell Weight) and AWT (Animal Weight) Table 2. Comparative statement of meristic traits of Thais species Characters T. lacera 5-6 7-11 T. bufo 5 9-11 T. tissoti 5 10-14 T. rudolphi 5 12-13 T. blanfordi 5-6 9-11 T. subnodulosa 6 10-12 No. of primary spiral cords on body whorl bearing tubercles 2 2 or 4 4 3-5 2-4 4 No. of ridges or teeth inside of outer lip of the aperture 0 0 4-5 26-29 4-8 4-5 No. of inner lateral denticles (radula) 1 1 1 1 1 1 No. of denticles between lateral and marginal cusps 5 7 3 6 6 1 Plain grayish or yellowish tan, inside of aperture pale orange light brown to gray in colour Light brown, with dark brown tubercles and aperture whitish Chocolate brown with white spaces between beads on the beaded cords aperture and columella white Light brown, interior white, dark blotches on columella chocolate brown with dark brown tubercles No. of whorls No. of tubercles in first spiral cord on shoulder of the body whorl Colour INDIAN J. MAR. SCI., VOL. 46, NO. 06, JUNE 2017 Results Based on our present findings six species of Thais are described below. T. lacera (Born, 1778) Fig. 1(A & B) Shell with 5-6 whorls, body whorl largest. Secondary spiral cords (8-12) present between first two well developed tuberculated primary spiral keels on body whorl. Umbilical chink surrounded by a broad thickened rim. Aperture ovate, inside of the outer lip smooth and siphonal canal short. Two grooved sulcus present instead of anal sulcus, where keeled spiral ridges ended on outer lip. Colour: Shell surface plain greyish or yellowish tan, inside of aperture pale orange, juveniles had darker lines in grooves on inner side of the outer lips. The radula with a triangular pointed central cusp; lateral cusps bear single inner lateral denticle; edge of the inner lateral denticle serrated; base of the inner lateral denticle wider, five denticles present between marginal and lateral cusps. The length of lateral cusp about half of the total length of central cusp. T. rudolphi (Lamarck, 1822) Fig. 1 (C&D) Shell thick with large body whorl, aperture more expanded with a short siphonal canal, four whorls, short conical apex, spiral growth lines well developed and aperture canaliculated both the ways. Surface sculptured with spiraled, widely beaded cords with plain spiral cords between. Columella almost straight, a longitudinal deep notch in middle region of anterior portion of columella is present. 4-5 flat but feebly raised spiral ridges on the body whorl, alternatively banded with white and dark brown nodules. Outer lip thin, inner surface finely grooved in brown and yellowish line with the outer fine spiral ridges. Columella and parietal wall heavily calloused and yellowish in colour but, inner margin of columella towards aperture dark brown in appearance. Umbilicus reduced. Colour: Chocolate brown with white spaces between beads on the beaded cords; aperture and columella white. Six denticles present between lateral and marginal cusps; first denticle on outer base of the lateral cusp smaller than other five denticles; a single inner lateral denticle; central cusp straight and pointed. The base of lateral cusp wider than central cusp. T. subnodulosa (Gravely 1942) Fig. 1 (E & F) Shell slender, spire longer than the body whorl; aperture opening narrow. The Body whorl consisted of a white band between the third and 1101 fourth row of tubercles, visible inside of the aperture. Aperture with four to five denticles, the posterior two denticles lead to raised ridges inside the aperture. Spire consists of five angulated whorls, with two spiral cords of compressed tubercles on each whorl. Body whorl bears 4-5 spiral chords of compressed round tubercles. Axial sculpture with 8-9 axial ribs. Denticles 4-5 inside of the outer lip of aperture. Columella with 2-3 anterior plications just above the siphonal canal; siphonal canal short and narrow; anal sulcus deep, inverted ‘U’ shaped. Colour: Shell chocolate brown with dark brown tubercles, Interior of aperture violet in colour. Columella with dark brown patch posteriorly, anterior portion violet in colour. Central cusp of radula was thin, needle shaped; 1 or 2 denticles present between lateral and central cusps; single marginal denticle. Marginal cusp absent. T. tissoti (Petit, 1852) Fig.1 (G & H) Spire elevated, body whorl large and oblong. Aperture narrowly ovate, outer margin crenulated, inside of the outer lip with 4-5 ridges, columella smooth plicated anteriorly, margined posteriorly by ridge, anal sulcus deep inverted ‘U’ shape. The sculpture of body whorl consists of 4 thick spiral ridges with bisulcate grooves and two narrow cords in between of primary spiral ridges ornamented with low tubercles, umbilicus small almost closed; anterior canal short. 10-14 tubercles present in first spiral row on shoulder of the body whorl. Colour: Light brown with dark brown tubercles and aperture brownish white in colour. Central cusp of radula triangular in shape and short; single inner denticle; four small pointed denticles between lateral and marginal cusps.The lateral cusps extending toward marginal cusp. Marginal cusp short and blunt. T. bufo (Lamarck, 1822) Fig.1(I & J) Shell thick, globose in shape, heavy and solid with short spire; body whorl largest with blunt spines. Aperture large and canaliculated on both anterior and posterior sides; columella broad, smooth and extended beyond upper extremity of outer lip. Umbilicus well developed and surrounded by thick umbilical chink. Aperture, relatively broader than other thaidid shells. The body whorl liraeted with fine spiral cords and spirally grooved structure. Outer lip margin serrated, alternately marked by white and brown spots but smooth inside. Body whorl wider, outer lip thicker, tubercles comparatively well 1102 KUMAR et al.: COMPARATIVE TAXONOMIC EVALUATION OF THAIS developed, widely spaced and less in number than T. rudolphi. Colour: The shell light brown to gray in colour. The rachidian cusp of radula sharply pointed; single inner lateral denticle pointed upward but slightly bent towards the lateral cusp. Seven denticles between lateral and marginal cusps, of which the first two denticles on outer base of the lateral cusp poorly developed and blunt (Fig 2). T. blanfordi (Melvill, 1893) Fig.1 (K & L) It neither pose bisulcate transverse groove nor the revolving raised ridges of small nodules equidistantly on the body whorl, as in T. tissoti. Spire made up of 4-5 angulated whorls, body whorls with two spiral rows of compressed tubercles (9-11 in numbers), and two rows of indistinct ridges, anal sulcus broad inverted ‘U’ shape margined by ridge. Inside of outer lip with 4-8 strong ridges, generally six, arranged in pairs. Anterior canal short and broadly open. Colour: Light brown, interior white, dark blotches on columella. A deep ‘V’ shape notch between inner lateral denticle and central cusp of radula. The central cusp pointed and slightly curved towards the right side. Six small pointed denticles between marginal and lateral cusp. Descriptive analysis of shell morphometric traits The mean shell length in the present study ranged from 45.17±3.13 mm in T. rudolphi to 18.14±0.29 mm in T. tissoti. The overall and species wise average of various morphometric traits is presented in Table1.In the present study, it was observed that the species belonging to the genus Thais have different radular morphological characters. The general radular formula for all Thaidid species was same, having rachiglossan type of radula consisting of one marginal cusp, one lateral cusp and one central cusp, but denticles present between lateral and marginal cusps differed in each species. The number of denticles between marginal and lateral cusps was found to be different in all studied species except in T. rudolphi and T. blanfordi, however, their radular morphology was different. The first denticle on outer base of the lateral cusp was smaller than other five denticles in T. rudolphi, but in T. blanfordi all denticles were similar in size. A deep ‘V’ shaped notch was present between inner denticle base of lateral cusp and central cusp in T. blanfordi, which was found to be a species specific character. Descriptive statistics of meristic traits The number of primary spiral cords on body whorl bearing tubercles in T. tissoti and T. subnodulosa were similar but, the number of whorls was different. The number of primary spiral cords on body whorl bearing tubercles was 2-4, 3-5, 2, 4, 2-4 and 4 in T. blanfordi, T. rudolphi, T. lacera, T. tissoti, T. bufo and T. subnodulosa, respectively. Number of body whorls in T. tissoti and T. bufo were found to be similar but different in presence and absence of ridges inside of the outer lip. They were also found to differ in number of the tubercles present on first spiral cord. The tubercles present on shoulder of the body whorl were 10-14 and 9-11 in T. tissoti and T. bufo, respectively (Table 2).The number of primary spiral cords (4) and number of ridges inside of the outer lip (4-5) was tissoti, but difference was seen in having six and found to be similar in T. subnodulosa and T.five number of whorls, respectively. T. lacera has unique meristic character as presence of only two keeled spiral ridges bearing strong triangular tubercles and absence of ridges inside of the outer lip. The PROC FREQ procedure was applied for meristic traits analysis revealed that in T. blanfordi 92% specimens were with 5 numbers of whorls, while 88% of T. lacerahad6 numbers of whorls. In, other three species i.e. T. rudolphi, T. tissoti and T. bufo 100% specimens were with 5 numbers of whorls, while 100% specimens of T. subnodulosa had six number of whorls (Table 3). Discussion Molluscs exhibit complex larval stages, frequent cryptic taxa and substantial phenotypic plasticity; all factors hinder morphological approaches to identify Thais species11, 12. The phenotypic plasticity in shell morphology which is common in molluscs poses additional problems for their proper identification and often leads to erroneous results creating many synonyms and doubtful species. In the present study, colour of the shells of same species was found to be differed along with their change in habitats. However, the morphological features used most frequently for species identification, including size, shape and the absence or presence of blotches on the nodules of shell surfaces and apertures etc. were highly variable depending on the local environment. INDIAN J. MAR. SCI., VOL. 46, NO. 06, JUNE 2017 1103 Table.3. Analysis of meristic traits by using PROC FREQ procedure Species Frequency of the meristic traits NO 5 6 2 4 4 6 8 9 NT 10 11 Freq (92%) (8%) (12%) (88%) (8%) (82%) (10%) (74%) (20%) (6%) 2 NO Freq 5 (12%) 6 (88%) 3 NO Freq 5 (100%) 4 NO Freq 5 (100%) 4 (100%) 5 NO Freq 5 (100%) 4 (100%) 6 NO Freq 6 (100%) 4 (100%) 1 NW NPBW NRL 2 (100%) 3 (10%) 4 (30%) 0 (100%) 5 (60%) 26 (20%) 27 (10%) 7 (14.6%) 28 (15%) 4 (6%) 29 (55%) 5 (94%) 0 (100%) 4 (50%) 8 (19.5%) 10 (26.8%) 12 (40%) 10 (4%) 10 (83.3%) 11 (24.4%) 13 (60%) 11 (10%) 9 (50%) 5 (50%) 9 (14.6%) 12 (8%) 13 (72%) 10 (30%) 14 (6%) 11 (20%) 12 (16.7%) SPECIES - 1 (T. blanfordi), 2 (T. lacera), 3 (T. rudolphi), 4 (T. tissoti), 5 (T. bufo) and 6 (T. subnodulosa) VARIABLES - NW (number of whorls), NPBW (number of primary spiral cords on body whorl), NRL (number of ridges inside of the outer lip) and NT (number of nodules/tubercles in first spiral row on shoulder). 1104 KUMAR et al.: COMPARATIVE TAXONOMIC EVALUATION OF THAIS The above studied six Thais species were identified based on the morphological and meristic traits along with their radular structure. The identification of Thais species is therefore still debated particularly on family and subfamily level. There are few genera under the family Muricidae i.e. Thais, Thaisella, Mancinella, Purpura, Drupa, Rapana and Indothais making muricids difficult to be identified. 3. 4. 5. 6. Conclusion The present finding will help in identification of Thais species. Though they are not important economically, occupy importance position in food chain of in intertidal ecology, as food for demersal fishes. They also help in assessing the environmental quality and often used as indicator species for many physicochemical parameters. Therefore, these organisms should be protected, conserved and managed for sustainable management of fishery resources. Acknowledgement Authors are grateful to Dr. W.S. Lakra, Director Central Institute of Fisheries Education for his encouragement and support during the study. 7. 8. 9. 10. 11. References 1. 2. 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